Switching device



Feb. 8, 1944. v F. KOPPELMANN SWITCHING DEVICE Filed March 4, 1941 Inventor Floris Kop elmahn His A Cornea.

Patented Feb. 8, 1944 UNITED STATES PATENT OFFICE SWITCHING DEVICE Application March 4, 1941, Serial No. 381,765 In Germany August 25, 1937 4 Claims.

The present invention relates to electrical switching devices and more particularly to improvements in switching devices of a character particularly adapted for use in connection with circuits for the conversion of direct current to alternating current or from alternating current to direct current.

In systems for the conversion of direct current to alternating current, or vice versa, utilizing mechanical switches the contacts are subjected to high speed operation and in order to eliminate sparking and provide long life for the contacts it is essential that contact bouncing be reduced to a minimum and the time of circuit opening and circuit closing be kept as accurately timed as possible with respect to th alternating current waves conducted by theswitching device. To accomplish these ends the presentinvention provides an improved switching device in which the movable contact element is mechanically separated from the contact operating means and its mass kept very low so that only a small operating force is required. Other features contributing to a reduction of contact bouncing, uniformity in time ofcircuit making and breaking and ease of adjustment. are embodied in the switch of the. present invention.

Itis an object of thepresentinvention to pro- .vide an improved mechanical switching device.

It is another object of the present invention to provide an improved mechanical switching device of simple and rugged construction characterized by consistent operation and long life under severe operating conditions.

It is another object of the present invention to provide an improved mechanical switching device of the type adapted for use in circuits for converting direct current to alternating current or vice versa, in which contact bouncing and sparking are reduced to a, minimum and the accuracs of timing of the opening .and closing ofga circuit is maintained for long periods without adjustment.

My invention will be better understood by reference to the following description taken in connection with the accompanying drawing, and.'its scope will be pointed out in the appended claims. In the drawing, Fig. 1 .is an elevational view partially in section of oneembodimentof my inven tion; Fig. 2 is a plan view of the movable contact assembly of the switch shown in Fig. 1; Fig. 3 is a plan view of the switch of Fig. 1 with the movable contact assembly removed, and Fig. 4 is a schematic illustration of an applicationof the. switch shown in J Fig. 1 to a circuit "fordcon- 1165 verting-three-phase,alternating current to direct current.

Referring now to the drawing, the illustrated embodiment of a switch structure embodying the present invention comprises a main'support or body 32 to the upperside of which is secured a plate .30 of insulating material. As illustrated in Fig. 3, the plate 30 is secured to the'body 32 by means of suitable bolts 36. Stationary contact blocks 29 of copper or similar material having good electrical conductivity, are secured to the insulating support 30 by means of bolts 3!. As shown in Figs. 1 and 13, the contact blocks 29 have the opposed faces thereof arranged in spaced relation to provide a, passage therebetween. Secured to the upper face of the blocks 29 adjacent the spaced edges thereof are silver inserts 20 and 2| having raised contact ribs along the opposed edges to form contact surfaces for a movable bridging contact 22 which is generally rectangular in shape and is preferably also of silver. Terminalsleeves 33are secured to the contact blocks 29 and provide means for-securing the conductors 34 to the switching device.

In accordance with the present invention the bridging contact 22 is made Very light and is mechanically separated-from the actuating means of the switch. As illustrated in the .drawingycontact 22 is carried by a spiralspring 23 interposed between the contact 22 and a transverse support 2 1. of insulating material. The support 24 is mounted on the insulating plate 30 by means of bolts 25 and cooperating nuts 26 and 21. The

bolts are positioned in holes 31 provided in the support 30 and secured thereto by suitable nuts (not shown). The spring 23 surrounds a small shoulder on the bridging contact to hold the lower end thereof in position relative to the con.- tact. The spring is preferably designed so that its is free from natural oscillations at the frequency at which the switch is designed to operate and is stiff enough so that no lateral bending occurs in the relatively short stroke of a few millimeters required of the bridging contact. It will be noted that with the above construction,

only the bridgingcontact 22 and spring 23 need be moved to operate the contact from one position to another.

In order to provide for a distributed application of the driving force an actuating rod or striker 35, preferably of insulating material, extends through an opening 38 in the plate 30 and between the opposed ends of the contact blocks 29. The striker is rectangular in cross section and'is recessed from itsupp'er end to provide two parallel striking edges which extend substantial- 1y parallel to the contact ribs of the stationary contact inserts 20 and 2|. In this way an actuating force parallel to the contact surfaces is applied to the bridging contact on each side of the point of application of spring pressure and in this way smoother operation of the bridging contact is obtained A second operating rod 40, arranged to oscillate and engage the striker 35, slides in a collar 4| supported from the body 32 by means of radial arms 42. By the interposition of the striker 35 of insulating material, particularly of the configuration shown, it is found that the tendency for the bridging contact to chatter is minimized and the sparking of the con tacts materially reduced. As shown in Fig. 4, the

arm 40 may be operated by any suitable means such as an eccentric 43 carried by a rotary shaft 44.

In Fig. 4 three switches embodying the present invention have been shown schematically connected in a circuit for transmitting energy between a three-phase alternating current supply circuit 9 and a direct current load circuit [0. As illustrated in the drawing, three switching devices are arranged with the operating arms extending radially with respect to the eccentric 43. The fixed contacts 20 of each of the three switching devices are electrically connected to gether and form one side of the direct current circuit is. The other side of the direct current circuit is connected with the neutral of the Y- connected secondary winding l2 of a supply transformer having the primary winding l I thereof energized from the alternating current supply circuit 9. A condenser l6 and damping resistor I! are connected across the fixed contacts 20 and 2i on each of the switches to minimize sparking at the contacts. As illustrated, the terminals 2| of each of the switches are connected to a different phase terminal of the secondary winding I2 through an inductive winding I4 associatedwith the closed core [3. The cores are of a material which saturates abruptly and are designed so that they are saturated except when the current through winding I4 is at a very low value. In this way a period of low current is interposed between the half cycles of the alternating current through the contacts, and substantially sparkless switching is accomplished as long as the timing of circuit opening and closing i accurately timed. Still further control of the impedance of windings l4 and in this way control of the current through the contacts -may be accomplished by the windings l which are connected in series and energized from a suitable source of direct current through an inductive element [8 and a variable resistor IS.

The arrangement shown in Fig. 4 is merely illustrative of the type of application for which switching devices embodying the present invention are well adapted and it is apparent-that certain features of the invention are capable of more general application.

While I have shown and described a particular embodiment of my invention, it will be apparent to those skilled in the art that changes and modifications may be made and I, therefore, aim in the appended claims to cover all such changes and modifications as fall within the true spirit and scope of my invention.

I claim:

1. A switching device for high speed periodic operation comprising supporting means having an aperture,a pair of stationary contacts mount.

ed on one side of said supporting means and each having a raised elongated contact portion, said contacts being mounted in spaced relation and with said contact portions in spaced parallel relation, a bridging contact spanning said raised contact portions in the closed circuit position of said switch, mean consisting only of a spring having a fixedly supported portion and a free portion engaging said bridging contact to bias the same to one circuit controlling position and of sufiicient stiffness to restrict lateral movement of said bridging contact when moved to a second circuit controlling position, an elongated operating member extending through the aperture in said support in a direction substantially perpendicular to said bridging contact for engaging said bridging contact, said operating member being mechanically separate from said support and said bridging contact and substantially unrestrained for movement into and out of engagement with said bridging contact, and means for operating said member periodically to engage said bridging contact to move it to a second circuit controlling position against the bias of said spring means.

2. A switching device for high speed periodic operation comprising a pair of stationary contacts each having a raised elongated contact portion, said contacts being mounted in spaced relation and with said contact portions in spaced parallel relation, a bridging contact spanning said raised contact portions in the closed circuit position of said switch, means arranged on one side of said stationary contacts providing a fixed support, means consisting only of spring means carried by said support and engaging said bridging contact between the raised contact portions of said stationary contacts to bias the same to one circuit controlling position, said spring means having sufiicient stiffness to prevent substantial 1ateral movement of said bridging contact when said contact is moved to a second circuit controlling position, an elongated operating member extending substantially perpendicular to said bridging contact and having portions of limited area extending parallel to said contact portions for engaging said bridging contact throughout substantially the full width thereof on the side opposite said spring and on opposite sides of the center of application of force by said spring means, and means for operating said member periodically to engage said bridging contact to move it to another circuit controlling position against the bias of said spring means.

3. A switching device for high speed periodic operation comprising supporting means having an aperture, a pair of stationary contacts mounted on one side of said support and each having a raised elongated contact portion, said contacts being mounted in spaced relation and with said contact portions in spaced parallel relation, a bridging contact spanning said raised contact portion in the closed circuit position of said switch, means arranged on one side of said stationary contacts providing a fixed support, means consisting only of spring means carried by said support and engaging said bridging contact to bias the same to closed circuit position; said and through the aperture of said supportmg means, said aperture and said member of insulating material having cooperating noncircular cross sections to prevent relative rotation therebetween, said operating member engaging said bridging contact on the side opposite said spring means, said operating member of insulating material having a portion of limited area extending parallel to said contact portion and on opposite sides of the center of application of force by said spring means, said operating member being mechanically separate from said supporting means and said bridging contact and substantially unrestrained for movement in a direction perpendicular to the plane of said bridging contact, and means for operating said member periodically to engage said bridging contact to move it away from said stationary contact against the bias of said spring means, said operating member being mechanically separate from said bridging contact to reduce the mass of the bridging contact assembly and thereby minimize contact bouncing during closing operation thereof.

4. A switching device for high speed periodic operation comprising a pair of stationary contacts each having a raised elongated contact portion, said contacts being mounted with the ends thereof in spaced relation and with said contact portions in spaced parallel relation, a substantially rectangular bridging contact spanning said raised contact portions in the closed circuit position of said switch, means arranged on one side of said stationary contacts providing a fixed support, means consisting of spring means carried by said support and engaging said bridging contact between the raised contact portions of said stationary contacts to bias said bridging contact to closed circuit position, said spring means having sufiicient stifiness to restrict lateral movement of said bridging contact when said bridging contact is moved to a second circuit controlling position, an elongated operating member of insulating material extending substantially perpendicular to said bridging contact and having spaced elongated bearing urfaces extending substantially parallel to the raised contact portions of said stationary contacts, said bearing portions engaging said bridging contact throughout substantially the full width thereof on the side opposite said spring means and on opposite sides of the center of application of force by said spring means, said operating member being substantially unrestrained for movement in a direction perpendicular to the plane of said bridging contact, and means for operating said member periodically to engage said bridging contact to move it away from said stationary contact against the bias of said spring means.

FLORIS KOPPELMANN. 

